The military warheads, such as those of missiles, rockets, etc., comprise pyrotechnic charges intended to destroy or damage a target located nearby. The activation of the charge is controlled by electronic devices embedded in the military warhead detecting the presence and the position of the target to be destroyed.
The military devices that include such pyrotechnic charges and their ignition devices are constantly changing to become more effective while offering a high level of vulnerability to external attacks, for example to the explosions due to the explosion of other charges, bullets, etc.
FIG. 1 represents a conventional configuration of a pyrotechnic charge with little vulnerability to external attacks.
In the configuration of FIG. 1, the pyrotechnic charge comprises an explosion-generating jacket 10 containing an explosive 12 having, in its central part, a sensitive pyrotechnic part 14, or detonator, which, when activated, for example by the sending of an electric pulse by a computation unit (not represented in the figure) determining the presence of a the target C, initiates the detonation of the explosive.
The ignition of the explosive causes the jacket 10 to explode producing bursts of explosions over a solid angle of 360°.
The effectiveness of such a pyrotechnic charge is low because the explosions are dispersed in all directions in space (arrows in FIG. 1) and few explosions are directed toward the target C.
However, this type of pyrotechnic charge of FIG. 1 offers little vulnerability to external attacks because the detonator 14 is at the center of the charge and the probability of its activation by an explosion or a bullet coming from outside is low.
FIG. 2 shows another embodiment of a pyrotechnic charge of the state of the art offering a better target destruction effectiveness.
In this embodiment of FIG. 2, an explosion generator 20 is placed at the center of an explosive charge 22 and multiple detonators 24 are distributed over the periphery of same explosive charge. A system for detecting the presence of the target triggers a single detonator 24 on the side of the charge 22 opposite the target C which propels all the explosions of the explosion generator 20 solely in the direction of the target (all the arrows in FIG. 2).
The advantage of this pyrotechnic charge configuration with selection of the detonator lies in its effectiveness in destroying the target but has the drawback of high vulnerability to external attacks. In practice, the probability of an explosion or another projectile reaching one of the external detonators 22, 24 on the periphery of the charge is fairly high.
In other military charge applications comprising an explosion generator inside the charge, the main explosive loading is ignited over a large surface area of the periphery of the pyrotechnic charge synchronously, instead of a one-off ignition as represented in FIG. 2.
For this type of ignition over a large surface area, the pyrotechnic charges of the state of the art comprise multiple ignition networks consisting of a distribution of multiple ignition points based on detonic distribution nodes.
FIG. 3 shows an embodiment of a pyrotechnic charge according to the technique of peripheral ignition of the explosive charge by a network of multiple ignition points.
In this embodiment of FIG. 3, an explosion generator 30 is placed at the center of an explosive charge 32. The surface of the charge is divided into n segments S1, S2, . . . Si . . . Sn each comprising an ignition network R1, R2, . . . Ri . . . Rn, each of the networks comprising a respective detonator Dt1, Dt2, . . . Dtn for its activation.
All the n detonators of the ignition networks covering the peripheral surface of the charge are remotely sited in a single smart safety and ignition device (with the acronym DSMF) (not represented in the figure).
As in the case of the pyrotechnic charge of FIG. 2, the presence of the target C triggers the detonator and the ignition network of the segment of the charge located opposite the target C propelling a maximum burst of explosions toward the target. The burst of explosions oriented in this way toward the target is all the more effective by virtue of the planar ignition of the network.
FIG. 4 shows a partial view of an exemplary embodiment of the pyrotechnic charge of FIG. 3, of cylindrical shape, through a network of multiple ignition points.
The pyrotechnic charge of FIG. 4 comprises a jacket 40, for example made of Plexiglass, of cylindrical shape surrounding an explosive charge 42 in the form of a bar. A synchronous ignition network Ri, of a segment Si at the surface of the explosive charge, produced in the cylindrical jacket 40 by a regular distribution of crossmembers 44 perpendicular to the surface of the charge and grooves 46 parallel to said surface comprising a detonation product intended to be initiated by a detonator (not represented in the figure) sited remotely from the ignition surface.
The crossmembers 44 form the multiple ignition points on the surface of the explosive which are linked by the ignition lines embodied by the grooves 46 containing the detonation product.
The detonation product in the grooves transmits a detonation wave initiated by the remotely-sited detonator, in the manner of a fuse, to all the ignition points distributed over the segment concerned of the jacket of the pyrotechnic charge.
The network must be produced by observing certain constraints. For example, the spacing between the various lines of the network comprising the detonation product must be such that these lines do not interfere with one another.
The number and the position of the ignition outputs at the level of the crossmembers (or multiple ignition points) are defined so as to generate an initiation of the detonation of the explosive charge that is totally synchronous over all the surface concerned of the pyrotechnic charge.
Depending on the sensitivity of the loading explosive of the pyrotechnic charge and its critical diameter, that is to say, the surface area dimension below which the detonation is impossible to initiate, it is possible to define an output geometry of the network such that a unitary detonation output is incapable of initiating the loading directly, in other words, such that it is necessary to superpose the effects of multiple detonation outputs to obtain the nominal ignition conditions for the explosive loading.
FIG. 5 shows a network with multiple synchronous ignition points of the state of the art.
The network of FIG. 5 comprises 64 ignition points pa distributed according to a regular pitch Ps over the surface of a segment Si of a pyrotechnic charge forming a square of 8 by 8 synchronous ignition points.
These various ignition points pa are linked, from a central distribution point Ps of the network, by detonation lines Cd, so as to provoke synchronous activation of all the ignition points. The distances traveled by the detonation wave between this central point Ps and the ignition points, along the detonation lines, are identical which ensures a synchronous detonation of the ignition points activating all the surface of the segment concerned of the explosive charge.
Nevertheless, this pyrotechnic charge configuration represented in FIGS. 4 and 5 offers an excessive vulnerability to surrounding attacks. For example, an impact on the surface of the pyrotechnic charge may accidentally initiate an element of the network (point or line) and generate a propagation of detonations within the network, ascending and descending with the risk of partially obtaining a synchronous output effect that is sufficient to ignite, in a quasi-nominal manner, the main explosive loading.
This peripheral network ignition design thus represents a weakness in the military charge which makes it incompatible with the modern reduced vulnerability munitions specifications.